This invention concerns a new class of reagents for use in the field of molecular biology and related areas of biochemistry. The wide and general usefulness of these reagents is based upon the widespread role of the divalent cations, magnesium (Mg.sup.2+) and calcium (Ca.sup.2+) in reactions involving nucleic acids. The magnesium cation in particular affects the annealing pattern of nucleic acid strands, the secondary and tertiary structure of DNA, RNA or RNA/DNA strands, and the properties of nucleotides which universally tend to complex with divalent cations.
In addition, divalent cations are of great importance in moderating the function of a wide range of nuclease enzymes which digest nucleic acid strands into their component monomeric nucleotides and nucleosides and are also important in the function of DNA and RNA polymerase enzymes which assemble DNA and RNA strands from their component nucleotides. The rate of function of nucleic acid polymerases, the processivity (tendency to continue forward reactions along a template strand), the accuracy, and the tolerance for improper or abnormal base sequences or substitute nucleotides are all well known to be affected by variations in the concentration of magnesium in the reaction medium.
It has been known for a number of years that various other divalent cations, most particularly manganese, could substitute for magnesium and essentially replicate its effects though often at somewhat lower concentrations. However, since magnesium is a convenient and inexpensive reagent, and since none of these cation substitutions achieved any biochemically novel or helpful additional result, there has been no industrial application of such substitutions. Further, many divalent cations of transition metals cannot tolerate the thioprotectants and reductants such as .beta.-mercaptoethanol and dithiothreitol (DTT) which are required by several of the polymerase enzymes for proper function, since these reductants tend to reduce and precipitate the transition metal cations.